The number and types of electronic devices available to consumers have increased tremendously the past few years, and this increase shows no signs of abating. Devices such as portable computing devices, tablet, desktop, and all-in-one computers, cell, smart, and media phones, storage devices, portable media players, navigation systems, monitors and other devices have become ubiquitous.
These devices often receive power and share data using various cables. These cables may have connector inserts, or plugs, on each end. The connector inserts may plug into connector receptacles on electronic devices, thereby forming one or more conductive paths for signals, power, and ground.
These signals are voltages that may vary relative to a ground line. The ground line may be referred to as signal ground. One or more signal grounds may be conveyed in a cable along with signals and supply voltages.
These signal grounds may become noisy. For example, frequency components from signals carried in the cable may corrupt the signal ground. Reflections caused by mismatched terminations may also degrade the quality of the ground. Also, signals outside the cable may send frequency components that are carried by the signal ground.
Enclosures or cases for electronic devices are often connected to ground. If a noisy signal ground connects to the device enclosure, the noise from the signal ground may radiate throughout the device, thereby degrading device performance.
To prevent this, circuitry to suppress electromagnetic interference (EMI) may be placed between a signal ground and an enclosure ground. But this circuitry may be bypassed if a signal ground is directly connected to the device enclosure.
Thus, what is needed are circuits, methods, and apparatus that may provide a separation between a signal ground and an enclosure ground such that EMI circuits are not bypassed.